Summary:
Sheep grazing is an important land use in the North-Atlantic region. This report presents an outline of presentations given at a workshop on the Sustainable management of sheep grazing in the North-Atlantic region in Trondheim on the 15 to 17 October 2007. Eleven
participants from Greenland, Iceland, the Faroe Islands and Norway
joined this interdisciplinary workshop, and the presentations focused on sheep grazing management, resource economy and ecology.

Summary:
In 2000 an enclosure experiment was established at one lowland ( 70 m a.s.l ) and one alpine (600 m a.s.l.) site in the Faroe Islands. After five years of enclosure, significant increases were seen in vegetation biomass at both altitudes as both the cover and vegetation height increased. Five species changed their abundance significantly. Only minor changes of species loss and gain were seen. Palatable grasses increased their abundance in enclosed plots, both at the lowland
and the alpine site.
Roots from Agrostis capillaris were examined for arbuscular mycorrhizal (AM) colonisation, and the colonisation found to be greater at grazed plots. The plant species that had a significantly negative response to grazing were typically classified as normally mycorrhizal, while species that proliferated in grazed plots were either classified as rarely mycorrhizal or as less palatable.

Summary:
The AM fungal communities of the Faroes were characterised. Open Top Chambers were used to examine the impact of passive warming, and from the same site samples were taken for a controlled warming experiment, looking at differences in root colonisation and fungal communities at a temperature close to the mean summer temperature in the Faroes, and another temperature within the upper limit of what is measured in the Faroes.
The main finding from this project is that arbuscular mycorrhizal (AM) fungi from the Faroe Islands respond to temperature, and do so in the same way as other field studies have shown: less root colonisation at elevated temperatures. When field samples were exposed to controlled temperatures in a laboratory, the results were not so conclusive, as there were considerable differences in colonisation responses from the different sites. However, pre-warming followed by low temperatures reduced colonisation, indicating that, after 2-week exposure to high temperatures, the fungi were not able to respond once low temperatures were restored.
There was evidence for a temperature-related change in the composition of the fungal assemblage in roots. Some of the fungal types were only found at low altitude. Moreover, species richness of the fungi was a function of the temperature range.
The impact of temperature on symbiotic function was examined in controlled conditions with a cultured fungal isolate. The main effect was that temperature increased fungal phosphate concentration, while arbuscule frequency was dependent on both substrate phosphate and temperature. Further there was a relationship between fungal sugars and arbuscular colonisation which implies that with more arbuscules the plant should receive more phosphate, and the fungus more sugars.